How Do Under Gravel Filters Work? | My Aquarium Club

Fish, like any other animal, take in food, water, and oxygen to maintain their metabolism and life. They also excrete solid and dissolved wastes. Those wastes are toxic to the animals that produced them. In the wild wastes are rapidly diluted by the much greater water volume to fish ratios there than those we use in out tanks. We are effectively concentrating the waste material, so we have to ensure that we can detoxify the waste in some manner. There are bacteria that are delighted to take fish waste and use it as their own food/energy source. The primary toxic nitrogen-containing waste product from fish is ammonia (NH3), or ammonium ion (NH4+), dependent on pH and temperature. Certain bacteria absorb ammonia/ammonium ion and get energy by oxidizing it to nitrite (NO2--). They release the nitrite as a waste product. Nitrite is as toxic as ammonia, or more so. Other bacteria take up nitrite and oxidize it to nitrate (NO3--), releasing the nitrate into the water. Nitrate is relatively non-toxic at low concentration. Both of these types of bacteria must live attached to a substrate, a surface. The largest surface area in our tanks is not the glass, but the gravel. The desired bacteria also require oxygen in the water, and as they are attached, water currents must bring the oxygen to them. The same currents will bring them "food" in the form of ammonia and nitrites- a good life if you are a nitrifying bacterium. Current can only penetrate a small distance into most gravel beds. Oxygen can penetrate by diffusion, but this is a much slower process than by current. This limits the oxygen- and food-rich sites to very near the surface. Okay, suppose we could arrange to have a slow current flowing through the bed, we would have the entire surface of the gravel open for bacterial colonization. From such thought came the undergravel filter.

Aquarium Undergravel Filters - Simple Filters for Small Fish Tanks & Fish Bowls

I have a theory that undergravel filters earned their poor reputation in the past, and mainly for symptoms relative to a fault which I have never even heard discussed: Conventional ones did encourage over-feeding, especially if there were bottom feeders in the tank. Any food that was targeted at bottom feeders was quickly sucked into the gravel and out of reach of the hungry fish where it fouled the filter media (gravel) prematurely and caused maintenance headaches. The lowest fish starved though plenty of food hit the bottom only to disappear into the gravel. I learned quickly it was better not to keep bottom feeders than to foul my undergravel filters trying to get enough food to them. For this reason I have had a decades-long happy affair with even conventional undergravel filters, though I am certain most aquarists continued to over-feed and hated them. Again, the advent of reverse-flow has totally eliminated even this problem for attentive aquarists.

Aquarium Filter Selection Guide: Undergravel, Power ..

Best undergravel filters for different fish tank sizes and using guide i have a 55 gallon fish aquarium, i just got in it i have 2 plecos, 2 cichlids, one swordtail and two dalmation mollies, i also just got two dragon fish. everything i have searched said either smooth gravel or sand would be best for the dragon fish. however i know there is a risk of dust from the sand which could effect the other fish, and i have an under gravel filter. my husband really would prefer to do sand over smother gem gravel as its cheaper for the size of tank we have... i was wondering is there anyway we can keep the gravel with the dragon fish without risk of them swallowing and choking on the gravel as they are filter eaters, and is there anyway sand would work with under gravel filter...?? please help

Aquarium Filter (Under Gravel Filter) Details - YouTube


Welcome to the Aquarium Undergravel Filters superstore! Undergravel filters offer one of the simplest ways to keep your pet's water properly filtered and aerated, while removing harmful contaminants and organic waste. The simple yet practical design features filter plates that utilize your gravel substrate as a source of biological filtration, pulling water through the gravel where beneficial bacteria can digest and eliminate harmful toxins and wastes. Undergravel filters are ideal for smaller aquatic tank setups, provide efficient filtration, and require minimal maintenance.

Pet Mountain's Aquarium Undergravel Filters store features top quality products from Lee's, one of the most trusted names in fish and reptile tank filtration and accessories. is the key to providing a strong biological filtration system. Undergravel filters utilize your tank's gravel substrate as a filtering surface area while providing oxygen to help aerate your aquarium water. Placed on the bottom surface of the aquarium, the filter plates utilize the gravel bed as a source of surface area and provide oxygen by recirculating the water down through the media and up through the uplift tubes.

allows you to maintain fish safely in a bowl or small designer aquarium for long extended periods of time. Keep your tank clean and aerated with this under gravel filter that minimizes maintenance responsibility. This filter includes a refillable carbon cartridge and decorative plant.

features a flat-plate design, meaning the filter plate has more open space which allows for better water circulation. It provides biological filtration & aeration for your aquarium water and includes a fish-saver elbow, Slim Discard-A-Stone, and Original Carbon Cartridge.


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Under Gravel Filter – A New Approach | The Aquarium Guide